Considering the card is specialized in multidisplay configurations that may not be the kind of issue you think it is. Bus width is not the only factor, memory speed is the multiplier. The card uses GDDR5 against slower memory on nvidia IIRC.
I think it is. The card drops out at high resolutions and cannot keep up with the 285 or the 295 (of course). To be fair the 295 IS two GPUs and so there was a recent test (PC Games Hardware) that compared the 5870 in Xfire to the 285 in SLI and the 5870 experienced severe stuttering. In AHII this will show up in even light dogfights and will get worse near CVs or fields with lots of AAA. The higher the resolution is pushed the larger the margin between the two setups and if you are using extreme resolutions with multi-monitors there is only one clear choice.
I cannot recommend the 295 to everyone. In fact if I were to buy again I would get two 275s and SLI them or maybe the 285s if they come down after Christmas.